PhD Student
Advisor: Ullrich Technau

Department of Neuroscience and Developmental Biology
University of Vienna

Abstract

Regenerative and developmental capacities in bilateral animals are often restricted to a specific stem cell lineage. However, in cnidarians, the phylogenetic sister group to all bilateral symmetric animals, the situation is more complex and diverse. Hydrozoan cnidarians possess a pluri- or multipotent interstitial cells that might be a derived feature and has not been identified in other cnidarians so far. In scyphozoan cnidarians, regenerative potential of tissues was identified in several different species but not specifically restricted to a certain stem cell lineage and hypothesized to rely on mechanisms like cell de-differentiation or trans-differentiation. Scyphozoan polyps show impressive tissue plasticity’s and regenerative capacities and undergo a metagenetic life cycle from an asexually propagating polyp to a sexual reproducing medusa. The medusa is characterized by specific set of cell-types that arise in the transition from sessile to free-swimming. Therefore, the question still arises, whether a specific stem cell line in these animals exists? Some old literature shows that isolated scyphozoan polyp tentacles can regenerate into entire animals. That is why the power to establish all polyp cell-types, as well as develop all medusa cell types must be intrinsic in an individual polyp tentacle. In this study, we want to survey and characterize the scyphozoan polyp’s tentacle as a powerful system to investigate the basics of both, regenerative as well as developmental processes in Scyphozoa. For the first time we did tentacle ablations for different cnidarian species to compare regenerative capacities of tentacles across all cnidarian clades, to show whether this trait is specific to the whole clade of scyphozoans. Further, we were investigating scyphozoan polyp regeneration using immunohistochemistry, fluorescent cell labeling, Edu cell proliferation assays and single-cell RNA sequencing and in situ hybridization to be able to identify a possible stem cell or precursor population for the neurosecretory as well as muscle cell lineages. To this end we looked at the consequences of the polyp’s tentacle loss for strobilation, the process that gives rise to the free swimming ephyra. We used immunohistochemistry as well as single-cell RNA sequencing for the readout of the resulting phenotype. We found that regenerating whole animals from isolated tentacles is a feature that is restricted to scyphozoan and cubozoan species. Furthermore, we can highlight that despite we could not identify a specific stem cell lineage the tentacle seems to act like an organizer tissue that influences cell fates and forms the foundation for regeneration and ephyra development.